This is a heavily used pair of US Army Mark 17 A1 observation binoculars, dating from around 1943-44. The Mark 17 was essentially a Mark 15 with the addition of the Mark 17 artillery adjustment reticle in the left eyepiece. There were 53,412 of them built by Westinghouse during the war using Bausch and Lomb or Optical Research Company glass elements. The stock number for this model, located on the right end cap, is 7578344. This M 17's coated optics place it in a time frame in both production and in development of binoculars and optics in general. The Army was looking for a means to allow their binoculars and telescopes to work earlier in the morning and further into twilight than the enemy's. They discovered that a coating of magnesium fluoride film applied under heat and vacuum allowed more light to pass and thus archieved their goals. By 1944 most Americam binoculars were made with coated optics.